Portable jib crane



Sept. 24, 1935. M. MOLINELLr PORTABLE JIB CRANE Filed March 24, 19:52'

[j: 7 Zwan/br Marzo M`0Z Patented Sept. 24, 1935 Appunti Maren 24, 1932, seria No. 601.013 1n Italy Maren 21, 1931 11 Claims. (Cl- 212-49) The invention relates to portable cranes such as are used for emergency jobs, as for rescuing trains, motor cars,l boats and the like,l or for building roads, railways and other buildings for 5 which it is not convenient to assemble a stationary crane, whilst one must hoist very heavy loads, as are posts of telephonic or electric lines, feeders, etc.

The scope of the invention is to provide an automatic control, adapted to quickly and surely displace the counterweght, so that the counterbalance be assured with any position of the jib and any load on the hook, comprised inside of the capacity of the crane.

Cranes are already known with automatic displacement of counterweght in accordance either with displacement of the load or with luiling of the jib or with increase of the load. With these cranes it is not possible to carry out a perfect balancing of load. Cranes are also known,

wherein the counterweght is driven by an electric motor, which, however, is controlled by hand.

Thus, it is possible, in theory, to keep a constant balance, but in practice this does not succeed at all. Balancing requires generally a skillful operator and it is not guickly regulable, so that the crane must be nevertheless givento a relatively high stability, which means a considerable weight.

The object of the invention is a differential mechanism adapted to control the motor accord-` ing to the actual momenta of load and counterweight, taking care of the own stability of the crane.

In carrying out the invention, the xed end of the hoisting rope, or the top pulley, islanchored to a lever being to the said fixed end of the rope at the same angle as the jib is to the vertical, while the counterweght, or a part 40 thereof, is slidable on another lever. The said levers form the end links of a chain actuating the switches of the motor, so that .the said switches are actuated by the differential action of the momenta of load and counterweght, `and control the motor in the sense of reestablishing the lost balance.

According to an embodiment of the invention a counterweght is provided, slidable on a rail at the side opposite to the jib and an auxiliary counterweght is slidable on a rocking rail and trailed by the former one. A transmission mechanism connects the rocking rail and a bell'crank lever adapted to compensate the inclination of the jib to a differential controller of a motor driving the counterweght and of a battery carrie'd .by me counterweght itself, auch um t varying of load or podtion thereof the counterweight is automatically deplaced, so as to carry l' out a perfect balance. Compensating means are provided for taking care of the weight of the l transmission links, and ,mayconsist of spring or counterweights, or both together.

The crane according to the invention has many advantages upon the cranes hitherto known. The differential control mechanism for the 1o counterweght permits to utilize the weight of this part in the mostuseful manner, since the position of the counterweght may be made to correspond at any minute to the position and magnitude of the load. The automatic control 15 permits to save the expense of an operator, the diierential action affords no lowering of the load for eiecting regulation, the lufilng of the jib does not call for any adjustment of'themechanism. Due to the compensatingmeans, the mechanism 20 kis perfectly balanced and of utmost sensibility.

The appended drawing illustrates diagrammatically a crane according to the invention, and

precisely is:

Fig. 1 a lateral viewof the crane, showing the 25 balancing mechanism.

Fig. 2 a plan of same,

Figs. 3 to 6 sectional views ofthe switching box, v .f

Fig. 'I a particular thereof in an enlarged scale. 30

According to the Figs. land 2, the crane consists of a xed superstructure I carried by a turntable base" 2 supported by the car and of a jib 3 'pivoted in I on the superstructure l and supported by links 5 pivoted on a slide 8.2 carried by as the superstructure and operated by a luillng screw 83 driven by a motor 8l, or in any other way. At the free end of the jib 3 a lset of pulleys S-Il is applied, carrying the hook or grip 'I, and the hoisting rope 20, xed at one end to a lever 2| 40 and wound about the pulleys 6,50, is secured to a hoisting drum 85 driven by a motor 86. At the other end ofv the rcrane a counterweght l is slidable, e. g. on rails 9 carried by the superstructure.

`These rails are provided with an indenture Il 45 meshing with a pinion 8B pivoted von the counterweight 8. The pinion 88 is driven through a connection 89 by an electric motor 90 located on the counterweght itself. Another small weight Il,

`trailed by the main counterweght l. slides on 50 railtracks Il pivoted in I2 on the superstructure and supported' in I3, e. g. through links I4, by

horizontal levers l 5 xed on a shaft IS journalled on the superstructure of the crane and carrying also a lever Il connected through a rod Il with 55 the differential controller I8. The fixed or standing end of the hoisting rope 28 is fixed to the arm 2| of -a bell-crank lever pivoted in 22 on the jib, whilst the other arm 23 of the said bell-crank lever is connected through links 24 to an amplifying lever 25 pivoted in 26 and connected through a rod 21 with arm 28 of a bell-crank lever situated at the lower end of the jib and pivoted thereon in 28. The other arm 38 of said lever acts against a tube 3| coaxial with the luiling pivot 32 of the jib, journalled in 4 on the superstructure. The tube 3| acts on the other end against a lever 33 flxed on a shaft 34 4carrying also another lever 35, which in turn is connected through a rod 86 with the differential controller I8.

Arm 2| of bell-crank lever 2|, 23 is made to be in its resting position parallel to the line connecting the pivot 4 of the jib and the axis of pulley 68, and the end of arm 2| is made to be almost coincident with the point of the periphery of pulley 68 where the rope 28 begins to wind itself thereupon, so that the rope 28 starts nearly vertically from arm 2|. For the sake of clearness, on the drawing the arm 2| has been drawn some considerable distance from this point. but it is intended that when hook 1 is in a position sufficiently far from pulley 68, the rope 28 is nearly vertical. However, generally speaking, the arm 2| of the said bell-crank lever could have any other position on the crane Aand any other inclination, provided that the angle between the rope 28 or the direction of effort exerted upon the said arm 2| and the arm itself be in any case and at any position of the jib equal to the angle of inclination of the jib, that is to the angle comprised between the vertical and line connecting pivot 4 and the axis of pulley 68.

The differential controller |8 consists substantially of a shaft 48 rotatably mounted in bearings carried by a frame 4|. On the shaft are fixed a plurality of contacting arms, whilst other arms are fixed thereto by means of elastic insets. A lever 42 transmits to the shaft the effort exerted by the hoisting rope through the rod 36; another lever 43 transmits the effort exerted by the weight I8 through the rod I8. The ratio of the said levers is such that the said efforts compensate each other when the counterweight and the load are perfectly balanced.

In order to effect the control lof the motor driving the counterweight 8 and as a consequence also the weight I8, which is rtrailed by the former through the joint 31, two contacts 45, 46 are provided, one for each direction of travel, operated by the shaft 48 through contacting arms 41, 48 fixed thereto, at least one of them being provided with an elastic inset, such that the shaft may rotate even when the said arm has fully pushed its contact.

The shaft 48 carries still another contacting arm, not shown, adapted to cut out the supply of current to the main circuit of the crane, when the momentum of the load is greater than that of the counterweight by. a predetermined amount. In such case all of the apparatuses stand still and lock themselves through their brakes, which are fitted with falling weights, so that no danger may arise to the crane.

Since in this condition the differential controller has the tendency to cut out the current as soon as the counterweight has reached its outmost position, whilst the crane has therein still a little stability, which it is .desirable to utilize fully, a spring 44 is provided. which is caught by another.

a lever 43 carried by the shaft 48 when it has accomplished the closure of the contact 46 for the outward motion of the counterweight. The spring 44 is intended to lock the rotation of the shaft 48, and as a consequence the cutting out 5 of the main circuit of the crane, until the momentum of the load has grown over that of the counterweight by an amount corresponding to the own stability of the crane.

The shaft 48 carries also, externally to the l0 frame 4|, an index, such that one may see at a distance what position the shaft is occupying; a handle carried by said shaft enables the operators to control by hand the movements of the counterweight and the main switch. A lock is l5 also provided, for locking said shaft 48 in each position, e. g. when one lets the crane be without survey, or when transporting it, in order to avoid the counterweight or any part of the crane to become unduly operative.

The embodiment of the differential controller or switching box illustrated in Figs. 3 to 7 consists of a case 38 provided with covers 38 and journalling the shaft 48. The shaft carries two operating cranks 5|, 52, and two controlling 25 levers53, 54, whilst a third controlling lever 58 isV loose thereon and suitable elastic means are provided for recalling said lever 55 into a resting position.

According to an embodiment (Fig. 7) the lever 30 54 is xed on the shaft 48 by means of a screw 16 and is provided with a resting surface 58. The lever 55 is loose on the shaft 48 and carries a projection 51 and a nose 58 facing the rest 58.

A spring 56 is tended between projection 51 and 35 lever 54 and presses lever 55 with its nose 58 against rest 58. The pressure is such that the effort normally exerted upon the lever 55 fork actuating the switch 68 is not sufcient for re- V moving the contact surfaces 58 and 58 from one 49' In the embodiment of Fig. 6 the spring 15 is wound about the shaft 48 and the operating cranks 5I, 52 are connected throughl links 6|, 62 to two levers 63, 64 pivoted in 65, 66 and suitably connected with the rods 36 and |8.

A crank 1| fixed on the shaft 48 carries a pin 8| moving freely inside of a bracket 18, which in turn is kept by a spring 18 pressed against two rests 18, 88. When the shaft 48 rotates by an angle greater than a given angle, the pin 8| 50 engages the bracket 18 and raises it from its rests 18, 88. Then the spring 18 exerts its braking action upon the shaft 48 and modifies the rating of the mechanism, such that a certain amount of overload is required on the hoisting rope for 55 effecting a further rotation of the shaft 48 and breakage of main circuit.

y All of the pivots and journal bearings are suitably tted with knives or ball races, in order to give to the mechanism a suicient sensibility, 80

which should however not be excessive, since in this case the counterweight would not remain still a minute and could also give rise to dangerous oscillations of the crane. In such instance one would be obliged to t a brake 11, suitably located inside of the casing 38, and acting on the shaft 48.

The levers 53, 54, 55 each actuate a switch 61, 68, 68, of which the first is inserted in the main circuit of the battery, the second is connected such as to give rise to an inward motion and the last is connected such as to give rise to an outward motion of the counterweight.

The working of the device is as follows: when the load on the hook 1 increases, the mechanism 75 'switch 5! and establishes the contacts relative,

thereto. Then the` motor of the counterweight starts up and the counterweight is driven astern until its momentum is equal to that of the load; then the spring of the switch 69 recalls the shaft 40 into the resting position, the circuits of the ino.- tor are cutout and the brake of the same locks itself, such that no further motion at all is possible.

When the load on hook 1 diminishes, the shaft I rotates in the opposite sense to that of the arrows, the lever 5l actuates the switch 58 and the circuit of the motor is closedv such as t0 move the counterweight towards the centre of the crane. As soon as the momenta of load and counterweight are equal, the spring of the switch 58 recalls the shaft 40 into its resting position, the circuits of the motor are cut out and the counterweig'ht remains at rest.

Should the load to be hoisted or the arm thereof be too great for the capacity of the crane,4 then the counterweight arrives at the end of its run without recalling the shaft 40 into its resting position. If the difference between'the momenta of load and counterweight in this condition does not exceed a predetermined value, corresponding to the momentum of own stability of the crane, then nothing else happens; but if this value is surpassed, then the shaft 40 is made to rotate further, against the action of springs and 55 (or 15), of brake 11, of Weights of the mechanism itself and counterweights 49, until lever 53 is pushed against switch 61, which cuts out the current and'stops the hoisting motor, whereupon its brake locks it, keeping the load suspended on the hook.

This device functions not only when the load to be raised exceeds the capacity of the crane, but also when the load increases very` rapidly, for example, if a. block of stone or iron is raised by-steel ropes or chains, or if a load is raised from water into air, as is the case when rescuing sunken boats, cars, etc. In such cases the load increases so quickly that the counterweight has not the time necessary for reaching the new balancing position before the ropes or chains have stretched out, and the crane would be overthrown, did not the main switch cut out the hoisting motor.

The shaft 40 carries at one end an index 12,

suitably shaped as a crank and provided with a knob 13 and a locking means, e. g. a push-button 14. Said index serves for indicating to the operator the position occupied by the shaft 40, and thus the ratio of load and counterweight momenta, as well as the operation of various parts of crane. By means of the knob 13 the crank 12 may be operated by hand, thus executing by hand the operations normally accomplished automatically.

By turning said crank against the action of springs 1li and 56 (or 15) in the utmost position, corresponding to an overload, the main circuit of the battery is cut out and all of the parts of crane are set at rest. The button 14 permits then to lock crank 12 in this position, thus avoiding any movement, either automatic or by hand. This is very useful when the crane should be abandoned or transported on any vehicle, to the purpose of avoiding an illicit use thereof.

The crane described and illustrated is intended to be indicated merely as an example and many modifications and various embodiments are poc'- sible within the scope of the invention, in accordance with the appended claims. Thus the main switch may comprise only the circuits oi.' come l motors, for example, ofthe hoisting, luiiing and sluing motors, or alternately the engine driving l the counterweight may be fed directly by the source of current.

I am aware that prior to my invention portable 10 cranes have been'made with counterweights displaceable so that their momentum varied in accordance with that of the load and also with counterweights slidable horizontally and such, wherein'the counterweight is driven by electric l5 motors, eventually contained therein with the battery and other parts; and therefore I do not claim such a combination broadly, but I claim:

1. In a portable crane, comprising a hoisting rope, rails, a counterweight slidable along said rails, a motor driving said counterweight and a diiferentialcontroller for said motor, a mechanism connected with said hoisting rope andsaid counterweight and adapted to exert upon said differential controller efforts proportionate to the momenta of the load on said hoisting rope and of the said counterweight.

2. In a portable crane having a jib adapted to be luifed, a hoisting rope, a counterweight, a motor driving said counterweight, and a differential controller for said motor, a mechanism adapted to actuate said diiferential controller in connection with the momentum of the load on the said hoisting rope, and .means adapted to compensate the eifect of luihng of the jib on momentum of load, so that the momentum of counterweight is in any oase equal to the actual momentum of load, no matter how the intensity of the load and its distance from the center of gravity oi' the crane vary.

3. In a portable crane having a jib adapted to be luifed, a hoisting rope flxed at one of its ends, a counterweight, a motor driving said counterweight and a controller for said motor, a mechanism adapted to actuate said controller in connection with the load on the said hoisting rope fixed at one of its ends, a bell crank lever pivoted on the said jib so that an arm of it is parallel to the jib and supports the xed end of the said hoisting rope, whilst the other arm of said lever is connected to the said mechanism.

4. In a portable crane having a hoisting rope, a jib adapted to be luifed, a counterweight, a link mechanism adapted to displace said counterweight in connection with the load onthe said hoisting rope and a lung pivot carrying said jib, a tube surrounding said pivot and forming a link of said mechanism, adapted to transmit ,motion along the said mechanism independently of the luiiing position of said jib. i

5. In a portable crane comprising a hoisting rope adapted to carry a load and having a fixed end, rails, a counterweight, slidable along said rails, a motor adapted to drive said counterweight, a plurality of switches for said motor, a 05 diierential mechanism connected with the fixed end of said hoisting rope adapted to actuate said switches so that the momentum of the counterweight be at any minute equal to that of the load on said hoisting rope, and a control member constituting a link of and actuated 'by said mechanism and adapted to operate said switches.

6. In a portable crane having a movable counterweight and an electric motor driving said counterweight, a set of switches adapted to energize said motor for a direction of rotation corresponding to drive-out said counterweight, another set of switches adapted to energize said motor for driving-in said counterweight, for a direction of rotation corresponding to driving-out said counterweight, another set of switches adapted to energize said motor for driving-in said counter-weight, a rocking shaft connected with load and counterweight and responsive to the difference between the momenta. of the load and of the counterweight, a lever moving with said rocking shaft and adapted to operate said first mentioned set of switches when the momentum of the load overcomes that of said counterweight and another lever moving with said rocking shaft and adapted to operate said second mentioned set of switches when the momentum of said counterweight overcomes that of the load'.

7. In a portable crane having a frame, a jib pivoted on and forming a part of said frame and adapted to have various inclinations to the vertical, rails fixed to the frame, a hoisting rope suspended at one of its ends, a counterweight slidable along said xed rails, a motor driving said counterweight, a controller for said motor, a lever pivoted on said jib and carrying the suspended end of said hoisting rope, the angle between said lever and said rope being at any moment equal to the inclination of the jlb to the vertical, a weight hauled by said counterweight, another lever pivoted on said frame along which runs said weight, and a diderential mechanism operatively connected with both of said levers and adapted 'to actuate said controller in accordance with the resulting momentum which tends to upset the crane. l

8. In a portable crane comprising a frame, a

jib pivoted on said frame and having an angleV of inclination to the vertical, a Vhoisting rope, rails pivoted on said frame, a counterweight movable along said rails, a motor driving said counterweight, and a controller for said motor; a differential member operating said controller, a lever fulcxumed on the crane, means connecting said hoisting rope and said lever, and adapted to exert upon said lever a force proportionate to the stress in the hoisting rope and at an angle equal to said angle of inclination of the jib, means connecting said lever and said differential member, and means connecting said rails and said differential member.

9. In a portable crane having a frame, a jlb pivotally mounted on said frame, a hoisting rope adapted to carry a load, rails, a counterweight movablealong Vsaid rails. aj motor drivingsaid counterweight, a group of switches for said mol tor, a shaft adapted to actuate said switches, and

means connecting said shaft, said counterweight and said rope, adapted to exert on said shaft a 5 momentum proportionate to the difference between the momentum of said counterweight and that of the load; abracket, an yabutment carried by said crane, a spring adapted to press said bracket against said abutment, and a pin carried by said shaft and adapted to loosely engage said bracket.

10. In a portable crane having a hoisting rope, an electric motor for winding said rope, a movable counterweight, a motor driving said counterweight, switches for said second mentioned motor, a main switch and a shaft operating said switches and said main switch; a crank keyed on said shaft, a pin carried by said crank and a -locking knob on said pin, adapted to lock said shaft in the position in which said main switch is opened.

11. In a portable crane having a hoisting rope adapted to carry a load, a plurality of mechanisms for causing movements of the load, multiple electric motors to drive the mechanisms that cause the aforesaid movements, rails, a counterweight running on said' rails, another electric motor driving the said counterweight, a set of switches adapted to energize the said last mentioned motor for a direction of rotation corresponding to drivingout of the counterweight, another set of switches adapted to energize the same last mentioned mo'- tor for driving-in of the counterweight, a rocking shaft connected with the load on the said hoisting rope and the counterweight, and responsive to the difference between the momenta of the load and of the counterweight, a lever moving with the said rocking shaft and adapted to operate with the first mentioned set of switches when o the momentum of the load overcomes that of the counterweight, another lever moving with the said l rocking shaft and adapted to operate the said second mentioned set of switches when the momentum of the counterweight overcomes that of the load, a general switch inserted in the feed circuit of all the motors and a third lever moving with the said rocking shaft and capable of openf ing the general switch when the equilibrium of the crane is compromised by the load in spite of the maximum shifting outside of the counterweight. l

. MARIO MOLI'NELLI. 

